Swedish researchers have found that women who smoke during pregnancy are likely to expose their children to the risk of diabetes and obesity later in life.

Researchers surveyed British data chronicling 17,000 people born during March 1958. Many of them were interviewed at age 16 and then again at age 33.

At birth, midwives collected information about smoking during pregnancy.

The scientists found:

• as young adults, some children of smoking mothers developed diabetes after the age of 16
• more than 600 were obese by age 33

Doctors say this means the children had a 30 per cent higher risk of developing diabetes or becoming obese.

The results are published in the current issue of the British Medical Journal.

Diabetes organizations say the findings are an important step in understanding the disease. It's not known what the causes are, but many experts believe it's a combination of genetic and environmental factors.

In their report, researchers say in utero exposure to smoking results in a lifelong dysfunction of the body's metabolism because the fetus is being malnourished or harmed by toxins in the cigarettes.

"More details are needed to clarify wether the association is really true," says John Wilding, a specialist in diabetes and obesity at the University of Liverpool.

"It's further reason to discourage women from smoking during pregnancy."